Light fast azoic pigments



NOV 6, 1951 H. T. LACEY ET Al. 2,573,851

LIGHT FAST AZOIC PIGMENTS Filed Nov. lO, 194'? Hkz/POL a r fra/fr BY' FAM/v p. noma/Pawn, d2 @WM/MVM ATTORNEY Patented Nov. 6, 19511 i j f- UNITED STATES PATENT oFFlcE LIGHT FAST Azolo PIGMENTS Harold T. Lacey, Marietta, Ohio, and Frank P. Dombroski, Jersey City, N. J., assignors to American Cyanamid Company, New York, N. Y., a corporation of Maine Application November 10, 1947, Serial No. 784,960

7 Claims. (Cl. 260-181) 1 2 This invention relates to a light fast form of of about 13.3 and a line of next greatest i11- the azo pigment obtained by coupling tetrazotensity at an interplanar spacing of 3.34 The tized dianisidine and the ortho-phenetidide of new crystalline form shows an extraordinary light 2,3-hydroxy naphthoicacid and to a process of fastness ranging from 125 to 200 hours on the making the pigment, which vpigment has the for- 5 fadeometer; that is to say, in the order of magni mula:

@NH NH O CH3 v O CH3 O11 v J) CO H502 The bright blue pigment referred to above is tude of from 5 to 10 times the normal light fastobtained in various forms depending on the conness of the amorphous pigment.

ditions of coupling of the tetrazotized dianisidine The process of the present invention in its With the coupling component. When this coubroader aspects is not limited to a particular pling is effected in the cold in alkaline medium, cationic surface active agent. In general, `catan amorphous product is obtained which has o ionic surface active agents are those which congood strength and brightness but very poor light tain a strongly active basic group which is a part fastness. A typical sample when subjected to of an amine, quaternary ammonium, amidine, light fastness tests in a fadeometershows marked sulfonium, or phosphonium compound. The fading after 18 to 20 hours. When the coupling group must be associated with sufficient nonis effected in the cold in acid medium a product o aromatic hydrocarbon groups to confer high suris obtained which for the most part is amorphous, face activity. Preferably these non-aromatic but contains certain crystalline impurities. This groupings should includea total of at least 8 or product has somewhat less strength but lsomemore carbon atoms. i what increased iight fastness of the order of The cationic surface active agents include about 4G hours in the fadeometer. Hot acid couamines with a suiiciently long hydrocarbon chain pling results in a crystalline pigment which is such as dodecylamine,hexadecylamine,octadecylvery weak, has ya light fastness of the order of amine, octadecylmethylamine, octadecyl dimethmagnitude of the amorphous product and has an ylamine and the like. These amines are usually X-ray diffraction spectrum which shows a line employed in the form of their salts such as sulof maximum intensity at an interplanar spacfates and chlorides which are for the most part ing in the crystal of about 9.2 and a line 0i 35 Water soluble. Y next strongest intensity at an interplanar spac- Another type of cationic surface active agents ing of 3.81 The deficient light fastness of the are those containing Quaternary ammonium radpigments prepared by the ordinary process deicals. Typical compounds are octadecyltrimeth-- scribed above greatly restricts their eld of y1 ammonium salts, beta-oleylaminoethyl triutility. methyl Iammonium chloride, 4-oleyl-aminophenyl According to the present invention, it is found trimethyl ammonium chloride, cetyl-benzyl vdithat a new type 0f Crystalline pigment is obtainmethyl ammonium chloride, and the like. The able when coupling is effected under acid condiquaternary radical may alsobe part of a heterotions in the presence of a cationic surface active cyclic compound provided there are sufficient agent 'and particularly COIldeIlSatn products of 45 non-aromatic groups to confer surface activity.

long chain alkyl substituted guanidines with eth- A typical example is cetylpyridinium chloride. ylene oxide such as for example the condensation Another type of cationic surface active agents of ethylene oxide with octadecyl guanidine. The are those of the amidine type. Typical comcoupling can be either cold or hot. This new pounds are stearamidine, octadecyl guanidinaf crystalline form of the pigment is entirely difoctadecyl isothiuronium chloride, 2 heptadecylferent from that obtained by hot acid coupling 1,3-dibenzylbenzimidazolonium chloride and the in the absence ofthe cationic surface active like.

agent. The crystal is characterized by an X-ray The preferred cationic surface active agents diffraction spectrum showing a line of maximum referred to above, namely thosewhich are reacintensity at an interplanar Spacing in the crystal o5 tion products :of ethyleneoxide with long chain,

alkyl substituted guanidines, are not limited to the ethylene oxide condensation product of the alkyl substituted guanidine with ethylene oxide but include also condensation products of other alkylene oxides. The best cationic surface active agent for the process of the present invention is the reaction product of octadecyl guanidine salts with about 6 moles of ethylene oxide. It should be noted that the octadecylguanidine salt does not have to be pure. On the contrary, the technical product prepared from mixed amines gives just as good results. This technical' product, while predominantly octadecylguanidine, contains some unsaturated products such as octadecenyl guanidine and also some substituted jguanidines with a hydrocarbon chain of 16 carbon atoms. Such a product is normally referred to as technical octadecylguanidine and Vth'isterm will be used through the specification in this sense.

The cationic surface active agent is usually emistics of the coupling solution.` In general,

amounts ranging from 'somewhatlesstha'n 10 to 30% of the weight of the pigment give good results. More cationic surface active agent does not do any harm, but as it does not improve the result, the additional cost is not justified.

While the present invention includes only one process of preparing the new form of the blue pigment, it is not limited as far as the pigment is` concerned to the method of preparation involving an acid coupling in the presence of. a cationic surface activeagent. On the contrary, it is vpossible to take a pigment which is not fast, for instance, one prepared by acid coupling in the cold in the absence of a cationic active surface agent, and transform it into the light fast crystalline form Vby heating ata temperature above the boilingpoint of waterand preferably below the point at which rapid decomposition takes place. When the Spigment madeby cold acidv coupling is so heated, the product obtained is substantially 'all of the light fast ycrystalline type defined above. Whenthe couplinglproceeds in alkaline medium, the heat-treatment, if continued for a suicient time, usually effects a marked improvement in light fastness, but sometimes does not transform all of the pigment intothe new crystalline form. These methods of preparing light fast blue pigments by heat treatmentare not claimedin thisiapplication-as they form the subjectmatter of the-copending application of Powell, Serial No. 785,191, -led November-10, 1947, which issued on AugustS, 1950, as Patent No. 2,517,924. However, since the v:light fast 1 crystalline pigment obtained by the high temperature process appears to be identical with that prepared by the acid coupling in the presence of' cationic active-'surface agent and. has the-same X-ray diffraction spectrum, the present invention is not limited as far as its product claims are concerned to any particular method of preparing the new crystallinepigment.

It is not desired to limitthe. presentinvention to any particular theory. However, -the following explanation appears to t the known facts.

Whenv the coupling component .i.s.precipitated .'m

dide ssubstantially identicali with thatfof. the.v

crystalline blue pigment obtained from hot acid coupling Without a surface active agent. The two crystalline substances are pseudomorphs. Photomicrographs show that the coupling occurs at the surface of the arylide crystals and proceeds by diffusion into the yarylide agglomerate which to all appearances remains lintact until reaction is complete. "Ihis` process of coupling at and through the crystal phase would be expected to limpose on the pigment the crystalline form of the arylide in a manner well known to crystallographers. 'Apparently that is what happens because when the arylide crystallizes under hot acid coupling, they pigment formed has the same X-ray dilraction spectrum as the coupling component. rIhisA crystalline form, produced by reason of their extraordinary constraint during formation' is 'of 'low photochemical and thermodynamic stability which results in its poor light f-astness. The cationic surface active agent appears to maintain thearylide in acid coupling in an amorphous -form during the.V coupling and crystals ofthe pigment `apparently then form in' the light resistant'crystalline'form which is' never obtained' under, ordinary conditions. This explanation of the function of'thesurface active agent may be incomplete because other methods of avoiding arylide crystallization such as adding an-alcoholic solution of the arylide directly to vthe tetrazorsolution-produce a-,pigment of low lightffastness.

The effector high-temperaturesdn 'transforming partly or completely the light unstable pigment form into the light stable `'crystalline form of the present .invention isprobably. ldue to the fact -that the-crystaljischangedby the high ternperature and. assumes the more light fastconfiguration.

The invention will be describedvin greater detail in conjunction -withlth'ei drawing which shows two vcurves of` X-raydiffraction spectra, the solid line being of. the lightlfastl pigment producedby the present invention fand. `the dotted line the.

light unstable crystalline pigment. obtained. by hot acid coupling.' This latter diffraction spectrum is substantially-the samelas.l that of. crystals of lthe 2,3.-hydroxy1naphthoic .acid o-phenetidide. The abscissael are of the. customary lnon-uniform scale of y interplana'rf crystal spacingas drawn by a recording spectrometer which uses a mechanically' movable Geigervcounter .and a balancing recorder. The vertical :scale-.is inpercent of the strongestlline. This has Inecessitated expanding the vertical-iscaleof the'dotte'd lnecurve as .the absolute intensity ofthe lineoffmaximum intensityat 9`.'2``A. "issomewhat less'than the absoute intensityl of thestrongestllinerof the solid curve. The figures-for`=thevariou's spectral lines ofv the solidand: 'dotted'- curves 'are -as follows:

The invention will be described in detail in the following specific examples in which the parts are by weight.

EXAMPLE 1 65.5 parts of 3,3dimethoxybenzldine are slurried with 3500 parts of water. 178 parts of 38% hydrochloric acid are added and the product stirred to complete solution at room temperature. The temperature of the 3,3dimethoxy benzidine dihydrochloride solution is then adjusted to C. and a solution of 39.0 parts of sodium nitrite in 390 parts of water adjusted to 0 C., is added rapidly with good agitation.' The resultging tetrazo solution is stirred at 0 C. until tetrazotization is complete. `An excessr of nitrous acid is preferably maintained `throughout the tetrazotizaton period. At the end of this time the mineral acidity of the tetrazo is neutralized by adding 75 parts of sodium acetate crystals.

An alkaline solution of 2,3-hydroxynaphthoic acid ortho-phenetidide is prepared by slurrying 173 parts of the phenetidide in 500 parts of water, adjusting the temperature of the slurry to 50"r C. and adding a solution of 39 parts of sodium hydroxide dissolved in 195 parts of water. This solution is alkaline to Clayton yellow paper. A sodium acetate solution, prepared by dissolving 100 parts of sodium acetate crystals in 500 parts of water is added. 5000 parts of cold water is then added and the temperature adjusted to 0 C. by adding ice. glacial acetic acid of 34.0 parts of the reaction product of octadecylguanidine carbonate with 6 moles of ethylene oxide adjusted vto 0 C., is added rapidly with good stirring to the alkaline solution of the 2,3-hydroxynaphthoic acid orthophenetidide. Precipitation results.

The resultant suspension of 2,3-hydroxynaphthoic acid ortho-phenetidide and the cationic agent is immediately added very rapidly with good agitation to the 3,3dimethoxybenzidine tetrazo solution at 0 C. and the charge stirred for several hours. The suspension ofv the blue pigment is heated up gradually to 90 C. and held at 90 until development is complete. The

A solution in 100 parts of l 25-50 hours in the fadeometer, whereas the tint of the pigment prepared with the above cationic agent shows such a remarkable improvement in light fastness that only a very slight fade in the fadeometer is observed after 200 hours. Substantially the same results are obtained with the cationic agent prepared from the reaction product obtained from technical octadecylguanidine which also contains some hexadecylguanidine.

The usual alkaline coupling without a cationic agent gives a strong reddish blue pigment which is very poor in light fastness .(the tint fades very badly in the fadeometer in 16 hours) Photomicrographs of samples of 2,3-hydroxynaphthoic acid ortho-phenetidide precipitated with and without the above cationic agent show that immediately after precipitation both samples are amorphous. After a few seconds the sample without the cationic agent begins to crystallize. Although the sample with the cationic agent slowly crystallizes, relatively smaller crystals are produced. The difference in crystal size is quite evident from microscopic examination. Immediate vcoupling of the phenetidide containing the cationic agent gives the greenish-blue pigment of remarkably improved light fastness as compared to the reddish blue fugitive pigment produced from the phenetidide precipitated without the cationic agent.

A comparison of the light fastness and physical properties of the blue pigment prepared according to Example 1 with the properties of the pigments obtained by acid or alkaline coupling without a cationic agent is shown in Table 1. Pigment A represents a pigment prepared by the conventional alkaline coupling in the absence of the cationic agent. Pigment B is acid coupled under the conditions described in the example except that the cationic surface active agent is omitted, and pigment C is thepigment produced by Example 1, pigment D is produced by hot acid coupling in the absence of -a cationic surface active agent, and pigment E is prepared by the method of Example 1 using hot acid coupling instead of cold acid coupling.

Table 1 Pigment A B C D E 1 Light astness 16-20 25-50 200 (approx.) 20 125-200.

(llajdeometer 5 rs. 2 Microscopic exam uo crystals (insolucrystals formed crystallization cr y s t a ls, and crystallization inatlon ol coution). very rapidly. slower than (B) slower than (B) pling composome crystals l..

crystals much smaller. mainly crystalline formed very rapidly.

mainly crystalline,

aud crystals much smaller. 'crystalline X-ray n ent. 3 X-ray study of pigment. crystals).

X-ray diffraction spectrum solid line of the drawing.

X-ray diffraction spectrum dotted line cf the drawing.

dillraction spectrum of solid line.

1 The crystals do not exhibit the diffraction spectra of pigment C.

positive test to alkaline R salt for excess tetrazo generally disappears at approximately 70 C. At this point the coupling is complete and the final developed blue pigment is filtered hot, washed free of acid and dried at C.

A cationic agent is essential for a bright, blue, fast-to-light product. When the coupling is made without a cationic agent, but otherwise using the same procedure, the resulting pigment is very dull and dirty when tested as a 50 to 1 zinc oxide reduction in varnish by rubout test The figures given for fadeometer time in cases A, B and D represent the time at which there was a definite and serious fading. In the cases of pigments C and E, there is a very slight change in color at about to 125 hours on the fadeometer. The change is barely detectable and for practical purposes is not significant. No further change in color takes place, and it -is possible that the slight change, which can barely be detected,`may be due to the presence of traces of and the tint shows an appreciable vfade after impurities which are notvlight fast.

Blue pigments wereprepared "following the pro-` cedure of Example 1', `but in place of th'ereaction product' of octadecylguanidine carbonate with ethylene oxide, corresponding'y amounts' of'other cationic agents were used. vTheA cationicragentsv have the following approximate chemicalconstituent: substituted amide of alkyl Y phosphate (12-carbons), substituted amide ofalkyl phosphate (18 carbons), cetylrbenzyl dimethyli ammonium chloride.

The resulting pigments wereA substantially. sim.-A Show.

ilar to thoseproduced by.Example..1. and. high. light fastness` EXAMPLE 3v 65.5 parts -of- 3,3 dimethoxybenzidine areslurried with Y3500 parts of water. 178 parts -ofr3&%-v

hydrochloric acid are added and the product stirred-to complete solution at room temperature.. The 3,3( dimethoxybenzidine-dihydrochloride. sor-.- lution is at roomtemperature, and a solutionof.- 39.0 parts of sodium nitrite in. 3.90y parts-of waterat room.temperature isadded rapidly with good.

agitation. The resultingl tetrazo. solution is stirred at room temperaturer until'.tetrazotizationl is complete. An excess. of; nitrous acidis prefer.- ably maintained throughout the tetrazotization period. At the end of this time ,the mineralacid-` sodium acetate solution, prepared by dissolving- 100l parts ofsodium acetate crystals in 500 parts of water is. added. 5000parts of cold wateris then added and thetemperature adjusted to 0- A solution in 100 parts of' C. by adding ice. glacial acetic acid of. 50.0 partsof: the reaction product of octadecylguanidine carbonate with 6 other. cationic. agents-1 were used.v TheV cationic agents. have the following approximate chemical constituent: substituted amide of'alkyl phosphate (12 carbons), substituted amide of alkyl f phosphate (18 carbons) EXAMPLE 5 300 parts,I of" pigment slurry prepared from o-dianisidineand 2=hydroxy3naphthoio ophenetidide by coldacid coupling, according to the procedure of Example 1 except that no dispersing, agentis usedyis removed from the coupling solutionH before filtration and placed inja glass-lined autoclave at200 C. for'one hour; The resulting pigment shows crystal character similar to Pigment C ofExample 1, and inthe fadeometerfshows slight fading after 125 hours, which does-not increase much up to 200 hours.

EXAMPLE 6 A specimen of pigment' prepared from o-dianisidineV and 2-hydroxy-3-naphthoic o-phenetidide bycold acid couplingaccording to the-procedure of Example 1, except that no dispersing agent is used, iseboiled in aqueous calcium chloride solution (B. P. 105 C.) for two hours. resulting pigment is of excellent light astness, though somewhat weaker and duller thanthe pigment.. of Example 6 conditioned by autoclavmoles of ethylene oxide adjusted to 0 C. is added.

rapidly with good stirring to the alkaline solution of the 2,3-hydroxynaphthoic acid ortho-phenetidide. The resulting suspension is heated to 95 C.

The heated suspension of 2,3-hydroxynaphthoic acid ortho-phenetidide is added very rapidly, with good agitation, to the heated'tetrazo solution. The coupling is complete in a short time. The temperature is adjusted to 90 C; :and held at 90 until development is complete. At this stage the nal suspended blue pigmenti-s ltered hot, washed free of acid and dried at 60 C.

In the above method of coupling at a high temperature, the cationic agent is necessary for a bright, light fast product. Without the cationic agent the'pigment. is dull; dirty,.reddish blue, weaker, and very poor in light. fastness;

coupling are even superior to those ,of1 the pig-- ment made by cold coupling and thesame excellent light fastness is obtained.

EXAMPLE 4 Blue pigments. were prepared following; theprocedure of Example 3, but inV place of .thereaction product of octadecylguanidine carbonate with ethylene oxide, corresponding vamounts of The. tinctorial properties of the pigment-,madegby hotV ing.

EXAMPLEA '7 65.5`parts of 3,3'dimethoxybenzidine are slurried' with 3500 parts of'water and 178 parts of' tation. The resulting tetrazo solution is stirreduntil tetrazotization is complete at 0"I C. An excess of nitrousacid isV preferably maintained throughout' the tetrazotization period. end of this time, the mineral acid acidity of the tetrazo is neutralized by the addition of 175 parts of sodium acetate crystals. An alkaline solution of the 2,3-hydroxynaphthoic ortho-phenetidide is prepared by slurrying 173 parts of the phenetidide with 6000 parts of water, adjusting the temperature to C. and adding a solution of 100 parts of sodium hydroxide in 500 parts of water. This. solution is alkaline to Clayton yellow paper. The temperature is then adjusted to 0 C. with icc.

The tetrazotized 3,3dimethoxybenzidine solution (0 C.) is added to the alkaline solution of 2,3 hydroxynaphthoic acid ortho phenetidide over a short coupling period, and the resulting coupling stirred for one hour. The pH of the coupling, which is approximately 11.0, is adjusted to 4.5,byj the addition of parts of glacial acetic acid. The suspension of blue pigment is heated pared crystalline' by couplingin the presence ofl a. surface active agent. The resultingproduct isv ofv excellent light fastness but slightly. weaker andi duller.l than .material preparedv according;r to

Example 1 or Example 5'.

The

At thev This application is in part a continuation of our copending application Serial No. 544,334, filed July 10, 1944, now abandoned.

We claim:

1. A light fast crystalline form of the pigment having the chemical formula:

O CH:

and characterized by an X-ray diffraction spectrum in which the line of greatest intensity is at an interplanar crystal spacing of 13.3 A, and the second most intense line is at an interplanar spacing of 3.34

2. A method of preparing a crystalline azoic pigment of increased light fastness which cornprises coupling under acid conditions tetrazotized 3,3dimethoxybenzidine with a freshly precipitated form of the o-phenetidide of 2-hydroxy-3- naphthoic acid, a coupling taking place in the presence of a sufficient amount of cationic surface active agent to produce a product characterized by an X-ray diffraction spectrum in which the line of greatest intensity is at an interplanar crystal space of 13.13 Angstrom and the second most intense line is at an interplanar space of 3.34 ngstrom.

3. A method according to claim 2 in which the cationic surface active agent is a reaction product of octadecyl guanidine with ethylene oxide.

4. A method according to claim 3 in which the reaction product is octadecyl guanidine with six mols of ethylene oxide.

5. A process according to claim 2 in which the o-phenetidide of 2-hydroxy-3naphthoic acid was produced by precipitation in the presence of a cationic surface active agent.

6. A method according to claim 5 in which the cationic surface active agent is a reaction product of octadecyl guanidine with ethylene oxide.

7. A method according to claim 6 in which the reaction product is octadecyl guanidine with six mols of ethylene oxide.

HAROLD T. LACEY. FRANK P. DOMBROSKI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Mosher, Proc. Amer. Assoc. of Textile Chemists and Coloristsl Jan. 20, 1941, pages 32 and 37. 

1. A LIGHT FAST CRYSTALLINE FORM OF THE PIGMENT HAVING THE CHEMICAL FORMULA:
 2. A METHOF OF PERPARING A CRYSTALLINE AXOIC PIGMENT OF INCREASED LIGHT FASTNESS WHICH COMPRISES COUPLING UNDER ACID CONDITIONS TETRAZOTIZED 3,3''-DIMETHOXY-BERZIDINE WITH A FRESHLY PRECIPITATED FORM OF THE O-PHENETIDIDE OF 2-HYDROXY-3NAPHTHIOC ACID, A COUPLING TAKING PLACE IN THE PRESENCE OF A SUFFICIENT AMOUNT OF CATHIONIC SURFACE ACTIVE AGENT TO PRODUCE A PRODUCT CHARACTERIZED BY AN X-RAY DIFFRACTION SPECTRUM IN WHICH THE LINE OF GREATEST INTENSITY IS AT AN INTERPLANER CRYSTAL SPACE OF 13.13 ANGSTROM AND THE SECOND MOST INTENSE LINE IS AT AN INTERPLANER SPACE OF 3.34 ANGSTROM. 